Feeling nostalgic about your skiing holiday? You can always buy a poster, says John Windsor - but it will cost you a lot more than a week in the powder.

Collectables of the future are notoriously difficult to spot, but whenever one emerges it seems obvious in retrospect. Christie's South Kensington is holding its first auction dedicated to ski posters on 6 February (10.30am). Hitherto, they have been scattered in South Ken's thrice yearly sales of 19th and 20th century posters.

Even Japanese buyers have been asking for condition reports on the posters. They are fascinated by British period style. It was the intrepid British middle class that founded the Swiss skiing industry in the last century. Winter tourism in the Alps is said to have gained popularity in 1864, when the owner of the Kulm hotel in St Moritz invited a group of British summer holidaymakers for a free holiday in January, promising them a month of sun. Klosters, now a favourite of the Royals, welcomed its first winter sports enthusiasts in 1904 and Murren, in the Jungfrau region, became the birthplace of the ski package holiday in 1910, when a British Methodist minister, Henry Lunn, founded the British Public Schools Alpine Sports Club and persuaded hotels there to open in the winter.

It all came to an end in 1929, when the stock market crashed. But now that the Brits are once again back in the money they want more ski holidays - and more ski posters as souvenirs.

South Ken auctioneer Richard Barclay noticed that the market for ski posters was perking up at last year's general poster auctions. He got on the phone to dealers and collectors and assembled 241 ski posters dating from 1895 to 1970 for the forthcoming first dedicated sale. Estimates range from pounds 200 to pounds 5,000.

So far, this is a relatively raw market, fuelled by nostalgic holiday skiers - the sort with Alpine chalets who want a colourful poster or two for their architect-designed kitchen. It remains to be seen whether they will absorb 241 posters in one go. However, astute promotion by a big London auctioneer tends to be self-fulfilling.

Until more discerning collector-investors enter the bidding in earnest, prices will remain unsettled. You might pick up an unrecognised rarity cheaply - or become embroiled in an expensive saleroom duel between bidders who are mad-keen to own a decorative old poster of their favourite resort, unaware that it is relatively common.

Nevertheless, the criteria of what makes a ski poster valuable are emerging. To invest, look for pre-war posters with obvious period flavour - that is, those showing people with period hairstyles, clothes and skis.

Those by artists whose names are already sought after by poster collectors have added value. By buying these, you can rely on the support of an established collectors' market that is forcing up prices for posters that qualify as art. Even the film poster market, hot for stars' names and sex-appeal, has developed an eye for French and Italian artwork.

For example, the colourful posters of the French Art Deco artist Roger Broders are already sought after, whether or not they show skiing. In the Twenties and Thirties he was commissioned by the Paris Lyon Mediterranean Railway (PLM) to help lure English-speaking tourists to French ski resorts.

His PLM colour lithograph Winter Sports in the French Alps of about 1930, which is cited in collectors' guides to posters, is estimated pounds 1,200- pounds 1,600 in the forthcoming sale. It has period people, including a young woman skier with late Twenties-style permanent-wave hair carrying old- fashioned wooden skis and, in the background, an old-fashioned puff-puff ski railway, ensuring cross-over interest from railway poster collectors. One sold for pounds 1,320 at a South Ken poster sale in 1994 and last October one was bid up to a whopping pounds 2,070. How many bidders still want one? And how many more copies are awaiting consignment to auction by eager profit-takers? In a new market like this, you can never tell. But this poster will always be a classic.

Similarly, the work of Francisco Tamagno (born 1851, date of death uncertain) is establishing a healthy track record. South Ken have estimated his turn of the century PLM poster for the Chamonix winter sports at pounds 2,500-pounds 3,500. It shows, suspended precariously in mid-air, a daredevil skiing couple in white winter woollies, she with bonnet and long skirt, both without ski poles. What might have happened to them is a good talking point that adds value. In the June sale last year, one fetched an astonishing pounds 4,830 against an estimate of pounds 1,800-pounds 2,200. This one is in better condition - but will it be fought over as fiercely? Someone, somewhere, could soon be kicking themselves.

And do you fancy a gamble on the ski bunny? Alex Diggelmann's poster of about 1950 shows St Moritz's emblematic rabbit haring down the piste. It is estimated pounds 500-pounds 700, indicating that the auctioneers consider last October's high price for one - pounds 2,070 despite creasing - was a furry freak. The trouble with rabbits is they breed.

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